Velocity modulator device

ABSTRACT

A velocity modulator device is provided for printer type supports driven by rotary members comprising at least one driving mechanism including a motor causing a rotary member to rotate by means of a resilient torsion bar, said mechanism having a mechanical resonance frequency F. In accordance with the invention, the velocity modulator device is characterized in that the motor is a low inertia direct current motor supplied by a periodic current of the frequency F, the intensity of the current being such as to periodically bring the velocity of the rotary member to zero, at the frequency F, without changing its direction the motion of said member, resulting from superposition of a rotary uniform driving motion and an oscillatory motion at the frequency F.

Arhan et VELOCITY MODULATOR DEVICE Primary Examiner-David Smith, Jr.

[75] Inventors: Roger Pierre Arhan, Belfort; Andre Assistant m Langer Roger Camille Lacroix, Cravanche, Attorney Agent or firm-Fred Jacob both of France [73] Assignee: Societe Honeywell Bull (Societe ABSTRACT Anonyme) Pans France A velocity modulator device is provided for printer [22] Filed: Mar. 23, 1973 type supports driven by rotary members comprising at 1211 .APPL 3441312 122 2 3325511125,1i$??$$,$a n olliisiiii torsion bar, said mechanism having a mechanical reso- [52] U.S. Cl 318/115, 101/93 C, 101/110 nance frequency F.

Cl. In accordance the invention the velocity [58] Fleld of Search 101/93 C, 93 R, 111; modulator device is characterized in that the motor is 31855111511021103,124,119,443,444 a low inertia direct current motor supplied by a 1 periodic current of the frequency F, the intensity of [56] References Cited the current being such as to periodically bring the UNITED STATES PATENTS velocity of the rotary member to zero, at the 3,309,988 3/1967 Touchman 101/93 c frequency 1 Without changing its direction the motion 3,556,003 1/1971 Soderstrom.. 101/93 C of said member, resulting from superposition of a 3,654,859 4/1972 Touchman 101/93 C rotary uniform driving motion and an oscillatory garanoff 1210/1413? motion at the frequency F, oss l 22 Claims, 25 Drawing Figures l 'l 1 1/ 97 l 1 i i 98 99 I I 94c A 1 IM I 9513 V SVRI Q I 95 I {9413 1 F 33A 1 I 1 W M. I 94A 91 I 3311 1 25 I SVM 92 SVB I 1 5V SVB l i 93 i PATENTEDNUV 5197 v v sum 1m a FIG.1b

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1 VELOCITY MODULATOR DEVICE BACKGROUND OF THE INVENTION The present invention concerns a speed modulating device especially intended for printing machines whose type carrier is driven by a rotating element. Of such carriers, one may mention type-carrying bands, belts of the timing belt type, or type-carrying wheels or disks, and drums.

These printers include a writing medium in front of which the type-carrier and a set of striking devices comprising striking motors pass. Each of these motors is capable of sequentially applying striking pulses sequentially to the characters by means of a striking hammer.

To accomplish high-speed performance (printing speed exceeding around 500 lines per minute) the movement speed of the type-carrier must be relatively high (on the order of several meters per second). This entails certain drawbacks. In fact, the type-carrier does not stop during the striking of the characters and continues in a linear manner in front of them at a high speed. Consequently, when a striking motor is set in motion, anon-negligible parallel force, acting in the same direction as the movement, is generated during the impact corresponding with the selected character which has the tendency of driving the writing medium in the direction of passing in a noticeable manner. This is obviously detrimental to the print quality.

Furthermore, any variation in the movement time of the hammer causes misalignment in the print, which is vertical if, for instance a belt or a type-carrying band is involved or horizontal in the case of a drum. Particularly, as far as printers with type-carrying bands are concerned, they possess other disadvantages due to the particular structure of these carriers. These bands are generally equipped with elastic tongues on one edge and the characters are positioned at the ends of these tongues. When a character receives the impact of a printing hammer then the tongue carrying the character deforms to enable the struck character to remain in contact with the hammer as long as the impact lasts. It is evident that if one wishes to have printing machines of high-speed performances with this sort of carrier, and to achieve this by raising the passing speed (5 or 6 m/s) the tongues are subjected to substantial stresses and the frequent repetition of these stresses may entail a reduction of their working life.

It is possible to remedy these drawbacks by imparting to the type-carrier a periodic movement effecting a series of advances separated by actual stoppages during which the angular speed of the rotating part which drives this carrier strictly cancels itself. The typecarrier then halts in such a way that a series of characters is in the print position. The striking hammers are then set in motion. Since the type-carrier is immobile there is no driving force and the print quality is superior to that which would resultif the stoppage of the typecarrier had not occurred.

Devices which make such movement possible are known. In one of them the driven part (for instance a type-carrying wheel) is part of a rotating system of a certain natural resonant frequency at which it is apt to oscillate around its axis of rotation. The movement is produced by an electro-mechanical assembly including parts intended to generate a uniform rotation for said system, and a magnetic oscillator intended to generate pulses which create oscillations in the driven part of a resonant frequency in such a way that the movements of oscillation and uniform rotation of the revolving system overlap, and that the driven part is subjected to a series of advance and stopping movements.

In another device, magnetic stopping media are mounted on the two ends of the drive shaft of a rotating drum. These media permit the alternate advance or delay of the revolving movement, due to a torsion of the shaft which causes its arrest and consequently that of the drum. While the preceding devices make an effective stoppage of the drivenparts possible, they are complicated and heavy from a mechanical view point, hence costly, and they are not conductive to accomplishing high-speed performance.

SUMMARY OF THE INVENTION The present invention corrects these disadvantages. It concerns a speed-modulating device permitting the performance of a periodic movement of a sequence of separated advances and effective stoppages.

The modulating device according to the invention includes at least one part revolving by the intermediary of an elastic torsion bar, said mechanism having a mechanical resonant frequency F. It is characterized in that the motor is one provided with DC current, fed by a periodic current of frequency F, the amperage of the current being set in such a manner that the speed of the rotating part cancels itself periodically at the frequency F, without changing direction. The movement of this part is the resultant of the overlap of a uniform driving movement of rotation and an oscillation movement at the frequency F.

According to a particularly useful embodiment of the invention the motor shaft is also the torsion bar.

In a particular design of the invention the modulating device also comprises a synchronous motor driving said drive mechanism for the uniform rotational movement. Said motor with DC. current provides the oscillation at the frequency F.

In another form of embodiment the modulating device comprises two identical drive mechanisms whose rotating part is a pulley, the two pulleys being linked mechanically by a belt, the rotational axes of the pulleys being parallel and the two motors being fed synchronously. Said belt could, for instance, be an endless type-carrier band for printers.

According to this last form of design, the drive movement by uniform rotation of the two mechanisms can be accomplished by an synchronous motor. In this case, the motors with DC. current only provide the oscillation movement at the frequency F.

In a specially noteworthy form of embodiment of the invention, said revolving part includes two pulleys of parallel rotational axes mechanically linked by a belt in such a way that the first pulley is connected mechanically to said torsion bar, driving the second pulley by means of a belt, that second pulley driving in turn a rotor of the same inertia as the rotor of said motor with DC current, by the intermediary of the second torsion bar. Said belt may be a type-carrying band for printers. It is particularly remarkable that in this last form of design, said rotor is the rotor of an electric motor driving said mechanism of a uniform rotational movement, said motor with DC. current furnishing the oscillation movement at the frequency F. This electric motor may be either asynchronous, with DC. current, or synchronous.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood by the following description, with reference to the attached drawing. This description offers for exemplary, not limitating purposes, a form of embodiment in accordance with the invention.

In the drawings:

FIGS. la and 1b represent in diagrammatic form the type-carrying band intended to be driven by the modulating device according to the invention;

FIG. 2 shows as a function of the time various forms of velocity rules intended to be followed by the modulating device according to the invention;

FIGS. 3a and 3b illustrate, at two successive moments in which the type-carrying band is immobilized, the relative position of the hammers and the tongues;

FIGS. 4a, 4b and 4c give three examples of curves denoting the position of a point on the type-carrying band as a function of the time;

FIGS. 5a and 5b present two principles of embodiment of the modulating device according to the invention;

FIGS. 6a, 6b, 6c and 6d represent four different forms of current intended to feed the rotor of the driving I motor with DC. current in the modulating device according to the invention;

FIGS. 7a through 7e present five different modes of design of the modulating device, whose principles of embodiment are given in FIG. 5;

FIG. 8 illustrates the rotor of the DC. current motor with its drive shaft;

FIGS. 9a and 9b exhibit examples of coupling methods between different component elements of the modulating device according to the invention;

FIGS. 10 and 11 represent two examples of the design of the control and regulation devices for a modulating device according to the invention; and

FIG. I2 shows the invention being applied to a drum.

. DESCRIPTION OF THE PREFERRED EMBODIMENT In the example of embodiment described here the speed-modulating device is intended to drive a typecarrier for a printer, such as an endless type-carrying band. Such a band 1 is shown in FIG. 1, FIG. la being a perspective view, and FIG. lb being a very schematic top view.

The band I is represented as mounted in the printing machine on two pulleys 2A and 28 whose axes Y1 and Yl and Y2 and Y'2 are vertical. To facilitate the understanding of FIG. la, only a part of the band 1 has been shown with type-carrying tongues 11 to 20, the latter being intentionally oversized in relation to the band 1 so as to make FIG. la more distinct. A certain number of hammers 21 to 30 have been illustrated in the same manner, very schematically in FIG. lb. The purpose of the invention is to have the device impart to the endless band 1 aperiodic movement in such a way that its speed cancels itself at regular intervals at moments in which the hammers are setin motion to strike the characters selected by the logic of the printer.-

The basic principles of the invention permit the determination of the oscillation amplitude of the velocity,

the'frequency of which is a function of different paramete'rs (pitch of characters, hammers, printing speed, jump time of paper) defining the printer, are discussed hereafter.

In FIG. 1b a point Q of the band 1 is assumed, for instance, to be located on one of the tongues 11 to 20. It is first assumed that the assembly (pulleys+ band) vibrates at a certain frequency F around the axes Y1 Y'l or Y2 Y'2 with a maximum velocity amplitude V Then, the speed VB of the point Q takes the form V, sin wt in which at 2 rrF.

It is now assumed that this assembly is driven at a constant velocity, V by means of a suitable device while continuing to be actuated by the above described oscillation movement. The point 0 then possesses a resultant velocity VB V+ V sin'wt. Such a velocity is represented by the curve VB] in FIG. 2. By continuing to 'maintain a constant mean velocity V, but by increasing the maximum velocity amplitude V of the oscillations, a quasi increasing movement of the band 1 may result. Thus the velocity of this band, shown in FIG. 2 by the curve VB2, cancels itself periodically at the frequency F and V =V (I). It is apparent that such a rule of velocity as a function of the time is particularly useful for an application in a printer provided that a position of the characters strictly in front of the hammers can be accomplished when the velocity of the band cancels itself, that is at the instants ti, ti 1, etc. (FIG. 2).

The printing may then occur at these instants, as illustrated in FIG. 3. The latter is a schematic perspective view showing the hammers 23 to 29 in the front, and the tongues 13 to 19 in the rear. In FIG. 3A the band is shown in the position which it occupies at the moment ti. The point Q belonging to tongue 15 is then positioned in front of the hammer 25. If one wishes to print the character corresponding with that tongue the hammer 25 is set in motion. In the same way, in FIG. 3b which represents the band in the position which it occupies at the instant ti 1 the point 0 is in front of the hammer 26 which is set in motion if one desires to strike the same character as previously.

If p is the distance between the hammers and T ti l ti the period of the function VB V V sin wt, it may be seen that according to FIG. 3 the point 0 shifts from one hammer to the other during one period.

Thus this distance p may be written:

If this condition (II) is met, the band thus shifts by a pitch p, p being the spatial period during which its speed completes a cycle of oscillation.

The function XB representing the position of a point Q of the band as a function of time is obtained by integration of the expression for the velocity which is:

One sets V ,w== a, a being the amplitude of the oscillatron movement.

FIG. 4 shows three curves representing three functions XBl, X82, and X83, of the position of a point Q on the band having the same mean'value V of the velocity (slope on the right OM). The value of the velocity resulting from the two movements is given at any point of the curve by the value of the tangent at the point under consideration. The problem which is posed here comes down to determining the points at which that tangent is zero. These curves are represented in the FIGS. 4a, 4b, and 4c, respectively. At too small an amplitude of oscillation, the band does not stop (FIG. 4a). At too large an amplitude (curve XB3) the band stops (point A), comes back (point B), stops again (point C) to depart again thereafter. Though the band could operate under the conditions defined by the curves X81 and XB2, it is clear' that the most favorable situation is the one shown in FIG. 4b (curve XBZ). FIGS. 4a and 4b correspond with FIGS. 2 and 3 (with the curve VBl corresponding to the curve X81 and with the curve VB2 corresponding to the curve XB2).

The set of conditions I and II, and the set II and III are identical, p is regarded as a data of the system and not a parameter. According to how the set l-II or the set II-III are viewed the following three parameters determine the system;

in the first case, V, V,,, F,

in the second case, a, V, F.

In the two cases, the value of V or F is a function of the performance desired from the printer. If one calls VI the printing speed (expressed in lines per minute), and TS the jump time, the time 1' necessary to print a line is equal to -r (60/VI) TS.

To facilitate the argument, it is assumed that the pitch p is the same for the hammers as for the characters, and that the band 1 includes several identical sets of N characters.

During the time 7 each of the N characters must pass in front of the same hammer. Hence:

V Nxp/r and F N/r In conclusion, the modulating device according to the invention must meet three of four conditions I to IV, these conditions not being independent.

A schematic diagram of the emgodiment of such a device is shown in FIG. 5. The mechanism of FIG. 5a includes a passive mass 31 of the mass PM, an active mass 33 of the mass AM, this mass being that of the rotor of a low inertia DC. current motor. These two masses 31 and 33 are linked by .a torsion bar 32 of the rigidity K. This mechanism represents, considering its movement around the axis YY, a mechanical oscillator whose resonant frequency F depends on the values of PM, AM, and K.

If this mechanism is actuated at the resonant frequency F the two masses 3] and 33 will vibrate in an opposite phase around the axis YY, as indicated in FIG. 5a by the arrows F, and F A simple manner of supplying oscillation energy to that mechanism is to reverse the current at the frequency F in the rotor of the motor with DC. current, the stator of this motor being a permanent magnet. Such a current is shown in FIG. 6a.

Evidently, to the extent to which the system is linear, the amplitude of the movement of the masses PM and AM is a linear function of the maximum current in the motor. By superposing on this current a DC. current one superposes a drive movement at constant velocity on the oscillatory movement and the mechanism will be driven round the axis YY at a velocity whose form is identical with that of the curves of FIG. 2.

Another solution consists in that the mean component V of the velocity is supplied by an asynchronous motor 34, as illustrated in FIG. 5b, so that the motor with DC. current of the rotor 33 provides only the oscillation movement. It is noteworthy that the drive occurs in the nodal point of the torsion bar 32 by means of an elastic coupling 35, but this arrangement is not exclusive since the action of the motor 34 can take place at any point of the torsion bar 32, and at the limit, in one of the ends of the mechanism by use of an appropriate mechanical linking system.

Five different types of design of the mechanism, whose principles are described in FIG. 5, are shown in FIG. 7.

The modulating device 4, illustrated in FIG. 7a, includes the typecarrying band 1, the two identical pulleys 2a and 2b, the identical torsion bars 32a and 32b, and the two identical motors with DC. current, which are represented by their rotors 33A and 338. Since the device 4 is perfectly symmetrical from the mechanical and electrical viewpoint one may divide it into two half devices 4A and 4B which are perfectly identical and constitute two mechanical oscillators having the same resonant frequency F. This frequency is a function of the inertias I of the rotor 33A or 333 and In; of the pulley set 2A the semi-tape 1A (or 23 18).

It is evident that the two oscillators have to oscillate synchronously and that the rotors 33A and 33B are thus fed in phase by the same periodic current of the frequency F, this current being of the type as illustrated in FIGS. 6b to 6d. The form and the nature of these currents is subsequently explained. Under these conditions the two motors with DC. current supply, at the same time, the unift m rotational drive movement at the mean velocity V and the oscillation movement at the frequency F.

The device 5, represented in FIG. 7b, is to a large extent identical, but exhibits the following essential difference. The rotor 33B is replaced by a rotor 33C of the same inertia. Only the motor 33A, therefore, provides the uniform drive movement by itself at the mean velocity V, and the oscillating movement at the frequency F, of the two mechanical oscillators 5A and 5B. FIG. represents a special case of embodiment of the preceding device 5. In that illustration the rotor 33C is the rotor of an asynchronous motor 34. This motor provides the uniform drive at the mean velocity V of the modulating device 6 under consideration by the intermediary of the bar 328, the motor 33A then supplying only the oscillation movement at the frequency F. It is self-evident that the asynchronous motor 34 may be replaced by any electrical motor capable of furnishing a uniform rotational movement, for instance a motor with DC. current (which would be preferably similar to the motor of the rotor 33A or a synchronous motor).

The modulating device 7, illustrated in FIG. 7d, is to a large degree identical with the device 4 of FIG. 7a, but there is the following difference. The uniform drive of this device at the mean velocity V is accomplished by the asynchronous motor 34 by means of a belt 36A or 36B at one of the nodal points 37A or 37B. The motors with DC current, whose rotors 33A and 33B are fed synchronously by the periodic current of frequency F, furnish only the oscillation movement of the device 7.

The device 8, shown in FIG. 7e is to a large extent identical with the device 5, but has the following difference. The uniform drive movement of this device at the mean velocity V is supplied by the asynchronous motor 34 by means of the belt 36A at the nodal point 37A. The motor of the rotor 33A then provides only the oscillation movement at the frequency F.

As far as the devices 4 and 5 are concerned, the drive and oscillation energy may be furnished in the form of any one of the three periodic currents l at the frequency F represented in FIG. 6b, 6c, and 6d, each of these currents having mean positive value of I One also may consider that each of these currents I is the sum of a DC. current of the amperage I M supplying the uniform driving energy, and of a periodic current of the mean amperage zero providing the oscillation energy.

The current, illustrated in FIG. 6b, is such that its positive maximum level lp is equal in absolute value to a negative maximum level I the current I being equal in the course of each period T to lp during a period t T/2.

The current shown in FIG. 60 is such that I [p for nT r nT+ T/2 and I= I for nT+ T/2 t(n +1) T with (1p) (1,) and n being a positive integer. The current, represented in FIG. 6d, is a sinusoidal current of the positive mean value I The oscillation energy of the devices 6, 7, and 8 is furnished in the form, for instance, of the current shown in FIG. 60, but could serve equally well for any periodic current of the mean value zero.

The mode of design of the mechanical link rotor from the motor to torsion bar is represented in FIG. 8. The rotor 32 as such, and the torsion bar 33 form a single piece. In this type of embodiment the rotor 33 is one having a printed circuit. This mode of design permits the use of printed circuits of a current make, and turns out to be much less costly. Furthermore, it offers the following qualities:

precise determination of the resonant frequency due to the elastic continuity of the torsion bar 32;

mechanical simplicity (one single element); and

perfect linearity of the system, since the amplitude of the oscillations stays practically proportional to the amperage of the current (within the limits permitted by the heating of the rotor).

A preferred coupling method of the invention, be-

tween the pulley 2 and the torsion bar 32, is represented in FIG. 9a. FIG. 9b shows a type of coupling between the torsion bar 32 and the asynchronous motor 34 (not shown), this being an elastic coupling. This illustration exhibits the belt 36A, and ball bearings 38. FIGS. 10 and 11 illustrate two different methods of design of the'electronic control and regulation system of the modulating device according to the invention.

The control of such a device implies that the printing conditions are permanently met, that is, that the group of equations I-II-lV as well as the group ll-IIl-lV be strictly satisfied, these equations having been defined previously. A different control and regulation system corresponds with each of these groups of equations, the system 9, represented in FIG. 10, corresponding with the group of equations l-lI-IV, the system 10 with the group II-IIl-IV.

The principles of the control systems 9 and 10 are discussed hereafter. They are based on the following condition: there is no relative movement between the pulleys 2A and 2B and the band 1. Measuring the speed of the band is thus tantamount to measuring the speed of one of the pulleys which is easily done by means of a revolution counter. The system 9, illustrated in FIG. 10, should meet these conditions:

a control loop for maintaining the velocity V constant when confronted by printing disturbances;

h aving a control loop for securing the condition V V by adjusting the maximum level of the pulsed current;

a device (me c hanical or electrical), supplying the frequency F V/p;

a control loop for the exact positioning of the characters in front of the hammers; and

the system 9 shown in FIG. 10 controls a modulating device of the same type as the device 6 represented in FIG. (a single motor fed by a DC. current).

This system 9 comprises the revolution counter 91, the circuit-peak detector plus filter 92, the low-pass filter 93, the comparators 94A, 94B, and 94C, the source of the pulsed current A, the source of the DC. current 958, the voltage-frequency converter 96, the typeposition indicator 97, the hammer-position indicator 98, and the phase converter 99. In FIG. 10, are also schematically illustrated the pulleys 2A and 2B, the tape 1, the rotor of the motor 33A, and the rotor 33C.

The system 9 operates in the following manner. The revolution counter 91 measures the velocity of the pul-. ley 2B and sends out a signal SVB which is directly proportionate to that velocity, hence proportional to the velocity of the band. This signal SVB is transmitted to the inputs of circuit 92 and of the filter 93, respectively. At the output of circuit 92 a signal SVM is received which is equal to the amplitude of the signal SVB and, therefore, directly proportional to the amplitude of the velocity modulation of the band. The signal SVM is sent to the first of the two inputs of the comparator 94A. At the output of the filter 93, a signal SV is received which is directly proportion al to the mean velocity V of the band I. This signal SV is transmitted, on the one hand, to the second input of the comparator 94A and, on the other hand, to the first input of the comparator 94B. A reference signal SVR is sent to the second input of the same circuit which signal is directly proportional to the desired mean velocity.

The comparator 94A compares the values of SVM and SV (thus of V and V) and sends an error signal E to one of the two inputs of the pulsed current generator 95A which modifies the amplitude of the current Ip. Th3 comparator 94B compares the values of SVR and SV and sends an error signal E, to the input of the source of the DC. current 95B which modifies the value of this current. The sum total of the currents 1 and lp is transmitted to the rotor of the motor 33A.

The voltage-frequency converter 96 measures the mean velocity V and emit s pulses VF at the frequency F of such a type that F V/p (relation ll). These pulses are delayed in a phase converter 99 in proportion to an error signal E sent by the comparator 94C which represents the gap between the position of the characters in relation to the hammers. This gap is measured at the instants in which the velocity of the type-carrying band 1 is zero. The phase converter 99 then sends a signal to the generator 95A, this signal enabling the adjustment of the current lp to the proper value of the frequency F.

The regulator system 10, illustrated in FIG. 11, corresponds to the set of equations ll-lIl-IV and must, there; fore, satisfy the equation a P/2 1r instead of V V. The other printing conditions to be met, hence the corresponding principles of design are the same as for the regulator system 9.

Thus, the system includes the same elements 91, 93, 94B, 94C, 95A and 958 to 99, as the system 9. Instead of the circuit 92, it comprises a circuit 102 converting the signal SVB in a signal AMP with AMP S VB/a which is directly proportionate to the amplitude of an oscillation movement of the band, 1, and instead of the comparator 94A, a comparator 104 compares the signal AMP with the signal SP which is proportionate to the expression p/2 1r, this comparator 104 sending an error signal E, to the generator of the pulsed current 95A.

It goes without saying that the invention is in no way limited to the driving of a type-carrying band mounted on two pulleys, but is equally well applicable to the driving of any revolving medium, whether type-carrier or not, such as a type-carrying wheel or crown according to the two schematic diagrams of F l6. 5 where the wheel (or the crown) constitutes the passive mass PM, the different methods of drive for the wheel being fully @EPRE LQMQ QUL'E QHPSEEPE QlELQQ LQiRQHEE) that is, a single motor with DC. current, fed by a periodic pulsed current of the frequency F, or a combination motor with DC. current (fed by a pulsed current of the frequency F) asynchronous motor.

The invention may also be applied to a drum. This respective mode of embodiment is represented in FIG. 12.

The drum 40 is rigidly mounted on two torsion bars 42A and 428. These two bars are linked mechanically with the rotors of motors with DC. current 43A and 43B and supported by bearing clocks 44A and 448. The rotor 448 may be replaced by a rotor 44C of the same inertia. This rotor 44C may, for instance, be a rotor of an asynchronous motor. It is clear that all methods of drive used for the drum 40 are identical with those used for the assembly (band pulley).

What is claimed is:

1. An intermittent motion system comprising, in combination:

a rotatable assembly having at least one rotatable member to which intermittent motion is to be applied;

a drive assembly for said rotatable device including a dc. motor having a rotor of low inertia and a torsion bar connecting said rotor to said rotatable member, the system consisting of said rotatable assembly and said drive assembly having a natural mechanical frequency F, said drive assembly including means for imparting a uniform rotational motion component of constant velocity V to said rotatable member and means for energizing said do. motor at said frequency F to impart an oscillatory motion component to said rotatable member having a velocity function equal to V sin wt where V is the maximum velocity of said oscillatory component and W= 2 77 F; and control means for controlling energization of said drhg: assembly to assure V is substantially equal to V. 2. An intermittent motion system as defined in claim 1 wherein said control means includes means for producing an output signal indicative of V and comparison means connected to said output signal for controlling energization of said do. motor such that V V 3. An intermittent motion system as defined in claim 2 wherein said means for imparting a uniform rotational motion component comprises a source of do. current connectd to said d.c. motor.

4. An intermittent motion system as defined in claim 3 wherein said rotatable assembly comprises a first pulley constituting said rotatable member, a second pulley coplanar with said first pulley an endless belt trained about said pulleys and bearing spaced printing elements thereon, a second torsion bar connected at one end to said second pulley and a rotor connected to the other end of said second torsion bar, said first and second torsion bars being similar and said rotor of the dc. motor and said rotor connected to the second torsion bar having similar inertias.

5. An intermittent motion system as defined in claim 4 wherein said control means includes means for controlling the phase of said energization of the dc. motor whereby said printing elements periodically come to rest at predetermined fixed points.

6. An intermittent motion system as defined in claim 2 wherein said control means also includes means for controlling the phase of said energization of the dc. motor whereby to adjust the relative angular positions at which said rotatable member comes to rest.

7. The intermittent motion system as defined in claim 2 wherein said means for imparting uniform rotational motion comprises a second electrical motor.

8. The intermittent motion system as defined in claim 7 wherein said second motor is connected to said torsion bar.

9. The intermittent motion system as defined in claim 8 wherein said second motor is connected to the nodal point of said torsion bar.

10. The intermittent motion system as defined in claim 7 wherein said rotatable assembly comprises a first pulley constituting said rotatable member, a second pulley coplanar with said first pulley, an endless belt trained over said pulleys and bearing spaced printing elements, a second torsion bar connected at one end to said second pulley and a second rotor connected to the other end of said second torsion bar having an inertia substantially equal to that of said rotor of the dc. motor.

11. The intermittent motion system as defined in claim 10 wherein said second rotor constitutes the rotor of said second motor. I

12. The intermittent motion system as defined in claim 10 wherein said control means also includes means for producing an output signal proportional to V and comparison means connected to said output signal for controlling the amplitude of said energization of the dc. motor.

13. The intermittent motion system as defined in claim 1 wherein said rotatable member is a typecarrying disc of a printing machine.

14. The intermittent motion system as defined in claim 1 wherein said rotatable member is a typecarrying drum of a printing machine.

15. The intermittent motion system as defined in claim 1 wherein said rotatable assembly includes an endless type-carrying band of a printing machine.

16. An impact printer system comprising a driven assembly including an endless band bearing spaced print- 5 ing elements and a pair of driven pulleys around which said endless band is trained;

a pair of similar torsion bars each connected at one end to a respective one of said pulleys;

a pair of rotors having similar moments of inertia and each connected to the opposite end of a respective one of said torsion bars,

means for rotating at least one of said torsion bars to impart thereto a uniform rotat ional movement component of constant velocity V; and

means for rotating at least one of said torsion bars to impart thereto a sinusoidal rotational velocity component of frequency F corresponding substantially to velocity V fr. which corresponds to the natural mechanical frequency of the impact printer system.

17. The impact printer system as defined in claim 16 wherein the means last mentioned imparts an oscillatory velocity function equal to V sin wt where W 2 1r F.

18. The impact printer system as defined in claim 17 wherein said last mentioned means comprises a dc. motor having a rotor constituting one of said pair of rotors.

19. The impact printer system as defined in claim 18 including control means for controlling the amplitude and phase of said oscillatory component periodically to arrest the motion of said printing elements at predetermined fixed points.

20. The impact printer system as defined in claim 19 including a second electrical motor having a rotor conmeans connected to said output signal for controlling the amplitude of said oscillatory component.

' DATED Claim 16, column ll, line 29, "to velocity 7 ft which..." shoulc' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,346,681 November 5 lg974 PATENT NO.

INVENTOR(S) Roger Pierre Arhan et a1 It is certified that error appears in the abo ire-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 3, column 10, line 22,, "connectd" should read connectedread --to velocity? which corresponds- Signed and Scaled this twenty-second Of July 1975 [SEAL] v Arrest:

RUTH c. msou Arresring Officer UNIT D STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3, 846, 681 DATED November 5, 1974 INVENTOR(S) Roger Pierre Arhan et al It is certifi ed that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 3, column 10, line 22,, "connectd" Should read connected- Claim 16, column 11, line '29, "to velocity \7 ft. which..." shoulc read --to velocity?! which corresponds". I

Signed and Scaled this twenty-second Day of Juiy1975 [sen] Arrest:

RUTH c; MASON c. mksmu. DANN ff Commissioner of Parent: and Trademarks 

1. An intermittent motion system comprising, in combination: a rotatable assembly having at least one rotatable member to which intermittent motion is to be applied; a drive assembly for said rotatable device including a d.c. motor having a rotor of low inertia and a torsion bar connecting said rotor to said rotatable member, the system Consisting of said rotatable assembly and said drive assembly having a natural mechanical frequency F, said drive assembly including means for imparting a uniform rotational motion component of constant velocity V to said rotatable member and means for energizing said d.c. motor at said frequency F to impart an oscillatory motion component to said rotatable member having a velocity function equal to VM sin wt where VM is the maximum velocity of said oscillatory component and W 2 pi F; and control means for controlling energization of said drive assembly to assure VM is substantially equal to V.
 2. An intermittent motion system as defined in claim 1 wherein said control means includes means for producing an output signal indicative of VM and comparison means connected to said output signal for controlling energization of said d.c. motor such that V VM.
 3. An intermittent motion system as defined in claim 2 wherein said means for imparting a uniform rotational motion component comprises a source of d.c. current connectd to said d.c. motor.
 4. An intermittent motion system as defined in claim 3 wherein said rotatable assembly comprises a first pulley constituting said rotatable member, a second pulley coplanar with said first pulley an endless belt trained about said pulleys and bearing spaced printing elements thereon, a second torsion bar connected at one end to said second pulley and a rotor connected to the other end of said second torsion bar, said first and second torsion bars being similar and said rotor of the d.c. motor and said rotor connected to the second torsion bar having similar inertias.
 5. An intermittent motion system as defined in claim 4 wherein said control means includes means for controlling the phase of said energization of the d.c. motor whereby said printing elements periodically come to rest at predetermined fixed points.
 6. An intermittent motion system as defined in claim 2 wherein said control means also includes means for controlling the phase of said energization of the d.c. motor whereby to adjust the relative angular positions at which said rotatable member comes to rest.
 7. The intermittent motion system as defined in claim 2 wherein said means for imparting uniform rotational motion comprises a second electrical motor.
 8. The intermittent motion system as defined in claim 7 wherein said second motor is connected to said torsion bar.
 9. The intermittent motion system as defined in claim 8 wherein said second motor is connected to the nodal point of said torsion bar.
 10. The intermittent motion system as defined in claim 7 wherein said rotatable assembly comprises a first pulley constituting said rotatable member, a second pulley coplanar with said first pulley, an endless belt trained over said pulleys and bearing spaced printing elements, a second torsion bar connected at one end to said second pulley and a second rotor connected to the other end of said second torsion bar having an inertia substantially equal to that of said rotor of the d.c. motor.
 11. The intermittent motion system as defined in claim 10 wherein said second rotor constitutes the rotor of said second motor.
 12. The intermittent motion system as defined in claim 10 wherein said control means also includes means for producing an output signal proportional to V and comparison means connected to said output signal for controlling the amplitude of said energization of the d.c. motor.
 13. The intermittent motion system as defined in claim 1 wherein said rotatable member is a type-carrying disc of a printing machine.
 14. The intermittent motion system as defined in claim 1 wherein said rotatable member is a type-carrying drum of a printing machine.
 15. The intermittent motion system as defined in claim 1 wherein said rotatable assembly includes an endless type-carrying band of a printing machine.
 16. An impact printer system comprising a driven assembly including an endless band bearing spaced printing elements and a pair of driven pulleys around which said endless band is trained; a pair of similar torsion bars each connected at one end to a respective one of said pulleys; a pair of rotors having similar moments of inertia and each connected to the opposite end of a respective one of said torsion bars, means for rotating at least one of said torsion bars to impart thereto a uniform rotational movement component of constant velocity V; and means for rotating at least one of said torsion bars to impart thereto a sinusoidal rotational velocity component of frequency F corresponding substantially to velocity V ft. which corresponds to the natural mechanical frequency of the impact printer system.
 17. The impact printer system as defined in claim 16 wherein the means last mentioned imparts an oscillatory velocity function equal to V sin wt where W 2 pi F.
 18. The impact printer system as defined in claim 17 wherein said last mentioned means comprises a d.c. motor having a rotor constituting one of said pair of rotors.
 19. The impact printer system as defined in claim 18 including control means for controlling the amplitude and phase of said oscillatory component periodically to arrest the motion of said printing elements at predetermined fixed points.
 20. The impact printer system as defined in claim 19 including a second electrical motor having a rotor constituting the other one of said pair of rotors.
 21. The impact printer system as defined in claim 19 wherein said means for rotating to impart a uniform rotational component comprises a source of d.c. current connected to said d.c. motor.
 22. The impact printer system as defined in claim 21 wherein said control system includes means for producing an output signal proportional to V and comparison means connected to said output signal for controlling the amplitude of said oscillatory component. 